Method and apparatus for mulching waste

ABSTRACT

Method and apparatus for processing green organic waste (hereafter “GOM”) into mulch particles for forming a mulch windrow including feeding means ( 11 ) for feeding GOM to a first cutting zone and rotating a plurality of blades ( 25 ) through that zone to cut the GOM into smaller particles, transferring the particles to a second cutting zone and rotating a plurality of blades ( 25 ) therethrough, to reduce their size to a suitable mulch particle size and ejecting the mulch particles at high velocity to form a windrow. The method and apparatus further includes the addition of moisture to increase the moisture content of the windrow formed.

The present invention relates to a method and apparatus for mulchingwaste material and is particularly although not exclusively concernedwith mulching of green organic material (GOM) for the purpose ofconverting that GOM into a form for composting. It will be convenienttherefore to describe the invention as it relates to that application,although it should be appreciated that the invention has widerapplication in the mulching of various waste products.

Green organic material is an expression adopted to cover a wide range oforganic waste and includes wooden waste products such as trees,branches, logs, grass cuttings, hard and croft woods and other foliage,but excludes treated wooden products. The disposal of GOM traditionallyhas been by way of dumping, such as into rubbish dumps or land fills, orif possible it has also been burnt off. However, in more recent years,GOM more and more is being treated to produce organic compost and thedemand for such compost over recent years has steadily grown.

Australian Standard 4454/1997 governs the characteristics preferred forcommercial sale of compost and that Standard covers a variety ofcomposting systems and products. The present invention is highlysuitable for producing compost through the open windrow compostingsystem and can meet the requirements of the Standard for that systemalthough it does have application to other composting systems.

Open windrow composting for GOM is known and normally involves treatingthe GOM in a manner which reduces the GOM into smaller particles andfeeding the treated product to a stockpile. The product is then screenedto eliminate particles which are too large for open windrow compostingafter which fertiliser is added and the product then windrowed. Thelarger particles which do not pass through the screen the first time areretreated to reduce their size and are then fertilised and windrowed asbefore. Most machinery manufactured for mulching GOM in the above mannerhas employed a hammer mechanism which applies a repetitive impact forceto the GOM so as to break it down into smaller particles. The particlesare collected, before being passed over sorting screens through whichparticles of the desired size fall. The process is continuous, so thatparticles which do not fall through the screens are returned for furtherimpact treatment before again being passed over the sorting screens. Theprocess continues until all the GOM has been converted to a size thatfits through the screens. When the particles pass through the screensthey fall onto a conveyor which transports the GOM to be windrowed.

A disadvantage with known mulching machines concerns the of use particlescreens. Such screens are commonly clogged over time by particles thatare small enough to be trapped by the screen, but which are too large topass through. Periodic cleaning or changing of the screens is thereforerequired and that creates downtime for the machine. The screens alsotend to limit access to the internal components of the machine, so thatmaintenance of the machine is made more difficult. A furtherdisadvantage relates to the product produced by such machines, becauseit is not in a form which can be windrowed without further treatment.Normally, the particles are required to the treated with fertiliserprior to windrowing, to produce mulch that will adequately compostaccording to the requirements for commercial compost as set out inAustralian Standard 4454/1997.

It is an object of the invention to overcome or at least alleviate oneor more of the disadvantages of the prior art. In particular, it is anobject of the invention to produce a mulch which can be windrowedimmediately and preferably without further treatment. It is a furtherobject of the invention to produce a mulch which has a controlledmoisture content and particle size.

According to the present invention there is provided a method ofprocessing green organic waste (hereafter “GOM”) into mulch product forforming a mulch windrow, including feeding GOM to a first cutting zoneand rotating a plurality of blades through that zone to cut the GOM intosmaller particles, transferring the particles to a second cutting zoneand rotating a plurality of blades therethrough to reduce their size toa suitable mulch particle size and ejecting said mulch particles at highvelocity to form a windrow, the method further including the addition ofmoisture to increase the moisture content at the windrow formed.

The present invention also provides apparatus for processing GOM to formmulch particles for a mulch windrow, said apparatus including a firstcutting zone and at least one blade for rotation through said firstcutting zone for cutting the GOM into particles, a second cutting zoneand at least one blade for rotation through said second cutting zone forcutting said particles to reduce their size to a suitable mulch particlesize, feeding means to feed GOM to said first cutting zone and ejectingmeans to eject said mulch particles from said second cutting zone athigh velocity to form a windrow, and means to increase the moisturecontent of the windrow formed by adding moisture.

The invention as defined above is distinguished from the prior art,because the mulch particles produced are of a size and moisture contentthat readily composts when formed into a windrow. Additionally, the useof the rotating blades as opposed to impacting hammers facilitatesreduction of the GOM without requiring sorting screens. The size of theparticles formed by the invention is partly a function of the speed atwhich GOM is fed to the first cutting zone, and partly a function of therotational velocity of the blades rotating through the respectivecutting zones. GOM can be processed at quite high speed. For example thefollowing feed speeds to the first cutting zone are appropriate

Larger material (150 mm-300 mm dia branches and twigs)−0.125 m/s

Medium material (150 mm-150 mm dia branches and twigs)−0.25 m/s

Small material (0.50 mm dia branches and twigs)−0.5 m/s

For the above feeding speeds, it is preferred that the blades rotate ata high speed in the range of 1600 RPM. Within these ranges, the particlesize of the GOM produced can be in the region of 0.50 mm which is anoptimum size for composting.

The addition of moisture to the particles ensures that the mulch productcan be produced with an optimum moisture content, preferably around 38%,conducive to composting. The moisture typically can be provided in theform of water and preferably is injected through water jets into theparticles in an evenly distributed manner. The water is preferablyinjected into the first cutting zone, although it may be injectedelsewhere. Preferably the volume of water injected can be controlled andvaried as necessary, so that variations in the moisture content of theGOM prior to mulching can be accommodated. Also, the water can containsuch additives as considered desirable for proper or optimum compostingof the mulch formed, such as nutrients.

It is a characteristic of the known machinery and methods that they donot, and largely cannot, add water. The reason for this, is that themulch product is delivered to form a windrow via a conveyor and thatdelivery does not facilitate addition of moisture. Additionally, thedelivery of the particle mulch in this manner also does not result in awindrow which is of a density achievable by the method and apparatus ofthe invention, as will become apparent later. The deficiency in moisturecontent and density can seriously inhibit the microbial activity withinthe windrow which is essential for composting. If the windrow is left inthis state for some time, it can possibly turn aerobic or anaerobicdepending upon the density thereof and that could cause pH imbalance ifthe windrow has proceeded to that state. The method and apparatus of theinvention can be used to correct this problem by re-mulching the windrowand adding correct nutrients just prior to re-mulching or by injectingwater during re-mulching.

The blades which pass through the first and second cutting zones can besupported on separate blade mounting arrangements which rotate aboutseparate axes. Preferably however, the blades are supported on a singleblade mounting arrangement which is arranged so that the blades passthrough both cutting zones, the zones being displaced from each otherabout the rotational path of the blade mounting arrangement.

The blade mounting arrangement can include any number of blades suitablyarranged relative to one another and it is possible that a single bladebe provided. However, it is preferred that a plurality of blades beprovided and in one mounting arrangement, a cylindrical cutting mill isprovided, which supports a plurality of blades extending both axiallythereof and extending outwardly beyond the circumference of the mill.Separate groups of axially extending blades can be disposed ofcircumferentially of the mill and in a preferred arrangement, fourgroups of axially extending blades are spaced equidistantly about themill circumference.

The blade or blades are preferably mounted for movement relative to thecutting mill and in one arrangement, they are rotatably mounted to thecutting mill. This ability to rotate reduces the potential for damage tooccur to the blades in the event that the GOM encountered is too hardfor the blade to cut, or if other GOM, such as metallic nails or rocksetc enter the cutting zones. Alternative arrangements, such as springmounting arrangements, are also appropriate for this purpose.

The transfer of particles from the first cutting zone to the secondcutting zone can occur in any suitable manner by any suitable means. Inone preferred form, the blades which pass through the first cutting zoneimparts a force in a direction which causes the particles to move intothe second cutting zone. Thus, the angle at which the blades engage theGOM at the first cutting zone may be such as to cause the particles tobe pushed toward the second cutting zone. Alternatively, or in additionto, guiding means may be employed. The guiding means may take the formof a guiding plate or plates, which direct the particles to the secondcutting zone.

The ejection of particles from the apparatus can be facilitated by anysuitable means. Preferably however, the blade speed through the secondcutting zone is such as to impart a velocity to the particles that issufficient for their ejection and for the creation of a windrow ofdesired characteristics. The velocity of the particles principallydetermines the density of the windrow and that velocity can becontrolled by altering the rotational speed of the blades through thesecond cutting zone. The density of a windrow formed by the inventioncan be greater than that formed by conventional means and occursprincipally due to the impact of mulch particles to progressively laidlayers of mulch. This arrangement is distinguished from the prior art inwhich the mulch, once prepared and treated, is laid in a windrow, notejected according to the invention.

Guiding means are preferably provided to guide the mulch particles inthe correct manner to form a windrow. The guiding means can include aplate which directs the mulch particles in the desired direction fromthe second cutting zone and that plate may be flat, or curved to form achannel and may be adjustable in the direction it guides the particles.In one form, the guiding means includes a delivery chute from which theparticles are delivered to form a windrow. The delivery chute can beformed to spread or to compact the mulch particles received from thesecond cutting zone and the chute may be adjustable to adjust thedirection at which the mulch particles exit the chute.

The apparatus of the invention is preferably portable and is preferablymounted on a trailer or formed with wheels. The apparatus preferably canbe trailed behind a car, truck or tractor, or includes its own motivecapability, so that a windrow of some length can be progressively formedby progressive movement of the apparatus.

The method and apparatus of the invention is such as to produce mulch ofa controllable moisture content which can be used to form a windrow forcomposting. Additionally the use of rotary blades at two separate zonesresults in an optimum particle sizes for composting without the need forparticle screens. The preferred aspects of the invention facilitate theformation of a densely packed windrow which can be formed in arelatively easy manner. The invention therefore has significantadvantages in the composting industry.

The attached drawings show an example embodiment of the inventionincluded in an assembly of the foregoing kind. The particularity ofthose drawings and the associated description does not supersede thegenerality of the preceding broad description of the invention.

FIG. 1 is a side cross-sectional view of an apparatus according to oneaspect of the invention.

FIG. 2 shows two views of a blade supporting hammer of FIG. 1.

FIG. 3 is a plan view of the rotary cutting mill of FIG. 1.

FIG. 4 is a side view of the rotary cutting mill of FIG. 1.

FIG. 5 is a further side view of the rotary cutting mill of FIG. 1,additionally showing associated components.

FIG. 1 shows a schematic cross-sectional view of a mulching machineaccording to one aspect of the invention. The machine 10 includes afeeding facility having an infeed conveyor belt 11 rotatable about aconveyer roller 12 which rotates in an anti-clockwise direction asshown. The conveyer roller 12 may be driven by any suitable drive meansand those drive means may be applied at any suitable location to drivethe roller 12, or another roller located at the opposite end of theinfeed conveyor belt 11 which is not shown in FIG. 1. The infeedconveyer belt 11 supports and conveys GOM which is to be treated by themulching machine 10.

The axis of the conveyer roller 12 about which the infeed conveyor belt11 travels is located substantially directly below the axis of theinfeed roller 13, which is also driven by suitable drive means, but in aclockwise direction as shown. The drive means can be arranged to driveboth the infeed roller 13 and the infeed conveyer belt 11 and such adrive means can be for example, hydraulically operated. Preferably, thedrive means provides variable speed drive and is reversible to clear GOMfrom between the infeed roller 13 and the infeed conveyer belt 11 if ajam occurs.

The location of the infeed roller 13 above the conveyer roller 12enables the GOM material passing the therebetween to be compressed priorto mulching. This compression serves to securely hold the GOM and toforce it through the feeding facility in the direction indicated.

In FIG. 1, the infeed roller 13 is shown to have a continuous circularoutline spaced above the conveyor belt 11, while a circular dot outlinespaced radially outwardly of the continuous outline is shown inengagement with the belt 11. The dot outline is indicative of aplurality of axially spaced rings 14 extending radially outwardly of theinfeed roller 13 and the edges of these rings are formed with axiallyfacing teeth. That arrangement enables the infeed roller 13 to grip theGOM between adjacent rings 14 and to cause it to be pushed or draggedbetween it and the conveyer belt 11 in the direction indicated.

One, or in some circumstances, both of the conveyor roller 12 or theinfeed roller 13 may be resiliently mounted, such as spring mounted, sothat any large and incompressible matter that finds its way between therespective rollers can pass through without damaging the roller. Thespring mounting may be made with traditional coil or cantilever springsor alternatively, a resilient rubber mounting may be provided.Alternatively, the infeed roller 13 may be mounted for substantiallyvertical movement when such matter is encountered, with return movementbeing under the effect of gravity. Other arrangements are also possible.

The infeed roller 13 is required to be of robust construction andpreferably is also of a material which is non-corrosive because it willbe exposed to moisture. Equally, the infeed conveyer belt 11 is alsorequired to be robust, as it will be exposed to high levels of abrasiveforce, particularly between the conveyer and infeed rollers.

GOM which passes through the infeed conveyer and rollers is engaged bycutting means in the form of a cutting mill 15. The cutting mill 15 isrotatably mounted and rotates in a clockwise direction as shown. Theaxis of rotation of the cutting mill is located between thecorresponding axes of rotation of the conveyer roller 12 and the infeedroller 13, although that positioning is a matter of design choice only.However, in the arrangement of the machine 10 as illustrated, theposition of the cutting mill 15 relative to the rollers 12 and 13facilitates a very compact arrangement.

The cutting mill 15 supports a plurality of cutting members in the formof cutting blade supporting hammers 16 and in FIG. 1, four of thesehammers are shown. It needs to be appreciated that the hammers 16 differfrom the hammers associated with previous mulching machinery, in thatthe hammers of the prior art applied only a crushing impact force asapposed to a cutting or slicing force. The hammers of the prior arttherefore have a different effect on the GOM compared to the hammers ofthe invention. FIG. 2 illustrates an individual hammer 16 in more detailand reference will now be made to that figure.

FIG. 2 shows two views of a hammer 16, namely a rear and a side view.From these figures, it can be seen that each hammer 16 includes a body17 and a depending arm 18. The body 17 is formed with an opening 31 toaccept a bush 19 and the bush 19 is provided to accept a mounting shaft19 a with which it is mounted to the cutting mill 15. The hammer 16further includes retaining means to retain a mulching blade thereagainstand the retaining means in part includes an abutment member 20 which isfixed by any suitable means to a peripheral surface 21 of the body 17.For example, the abutment member 20 may be fixed to the surface 21 bywelding, or by a bolt fastener. A rear surface 22 of the abutment member20 is spaced from a leading surface 23 of the depending arm 18, adistance sufficient to snugly receive therebetween a bottom end 24 of amulching blade 25. In order to accommodate blades of differentthicknesses, the abutment member may alternatively be adjustably mountedto the peripheral surface 21.

The blade 25 is further secured to the hammer 16, by releasable means inthe form of a nut and bolt fastener 26 and 27. The threaded bolt 26extends through an opening 28 in the depending arm 18 and is releasablyengaged by the nut 27. The opening 28 is countersunk to accommodate thebolt head 29 and the bolt head includes a notch to accommodate a weldedbutton 30 which is formed within the countersunk portion of the opening28 to prevent rotation of the bolt 26.

The above arrangement securely locates a mulching blade 25 relative tothe hammer 16, in a manner which facilitates quick and easy release ofthe blade when necessary due to wear or damage. Clearly however, otherarrangements could be employed to secure a blade to the hammer and thesearrangements are within the scope of the invention.

Each hammer 16 is secured to the cutting mill 15 in the followingmanner. Bushes 19, are inserted into the opening 31 formed in the body17 of the hammer 16 and each hammer 16 is placed between a pair ofsupporting plates 32 (see FIG. 3). This arrangement of the bushes 19 canbe seen in FIG. 2, which also shows that the bushes 19 are separated bya gap 32 a.

The opening 31 of the hammer 16, is aligned with corresponding openingsformed in the supporting plates 32 and the shaft 19 a is insertedthrough the pair of bushes 19, and between the pair of supporting plates32 through their openings, to locate the hammer 16 thereto. As will bediscussed later, the hammers 16 may be so mounted as to be rotatableabout the shaft 19 a, or so as to be fixed to the shaft 19 a whichitself is rotatable within the opening 31.

The figures showing side views of the cutting mill 15 show that a hammer16, or more correctly a row of hammers 16, are positioned in eachquadrant of the cylindrical mill 15. A single shaft 19 a provided foreach quadrant can be used to locate each hammer or row of hammers in thecutting mill 15, by that shaft extending between opposed sides of themill. The shafts 19 a are not shown in FIG. 3 but these would extendbetween opposite end supporting plates 32 a and 32 b, and would locateeach of the hammers 16 therebetween and as discussed above, the hammers16 can each rotate between the supporting plates 32. The shafts 19 a canbe fixed in place against a pair of end supporting plates 32 b and onearrangement suitable for that purpose is shown in FIG. 4. The fixingarrangement includes a fixing member 33 which has an opening 33 athrough which the shaft 19 a is received. A circlip arrangement, or anyother suitable arrangement can be employed to fix the shaft 19 arelative to the fixing member 33. The fixing member 33 is located on theouter side of the end supporting plates 32 b and includes a pointed end34 a that is configured to be received within a cavity 35 of a plate 36which is fixed to the outer surface of the end supporting plates 32 b byany suitable means such as welding. Receipt of the shaft 19 a within theopening 33 a of the fixing member 33 can be such that the shaft is fixedagainst rotating relative to the cutting mill 15. In that arrangementthe or each hammer 16 can, as discussed earlier, be arranged to rotaterelative to the shaft 19 a and this rotation of the hammers can preventor minimise damage that might otherwise occur to the blades whenperforming a cutting action if the product to the cut is too hard, suchas a nail or rock. In that case, the hammer 16 can rotate in theopposite direction to the rotation of the cutting mill 15 and allowpassage of the object through the machine 10 without, or with minimumdamage to the blade.

As seen in FIG. 3, a plurality of hammers 16 are spaced axially acrossthe cutting mill 15. Each hammer 16 is fixed, as described earlier,between a pair of supporting plates 32 and each pair of supportingplates is also spaced apart. The supporting plates 32 are formed in eachquadrant of the cutting mill 15 as a segment of a circle and are fittedto the cross-members 15 a of the cutting mill 15. (see FIGS. 1 and 4).The separate rows of cutting hammers (of which in FIG. 3 only two rowsof the four which can be seen in the side views of FIGS. 1 and 4 areshown), are axially displaced so that the gaps 37 between pairs ofsupporting members 32 of one row, are aligned with the hammer 16 of anadjacent row. In practice, each of the gaps 37 may be covered or closedat their open end, ie at the circumference of the cutting mill 15, bycurved cover plates of the same radius as the end supporting plates 32 bso that material to be mulched is prevented from entering these gaps.

As seen in each of the FIGS. 1, 2 and 4, in side view, the hammer 16 hasa particular shape, but that shape is not of significant importance tothe present invention. Indeed, the hammer 16 could take a variety ofshapes, which function in the required manner. The particular shapeshown causes the blade to be exposed beyond the outer circumference ofthe cutting mill 15 when the mill is rotating during operation of themachine, because of the weight distribution of the material forming thehammer. However, the hammers remain rotatable about the shaft 19 a sothat hard objects can be passed through the machine 10 without damage tothe blades 25 as discussed earlier.

The exposure of the blades 25 beyond outer circumference of the cuttingmill 15 is shown in FIG. 1, but is more clearly shown in FIG. 4. Inthese figures the hammers 16 are disposed in the cutting mill 15 in amanner that exposes the top end 38 of each blade 25 beyond the outercircumference of the mill 15. An outer portion of the depending arm 18of the hammer 16 is also exposed but this need not necessarily be thecase and will be at least partly dictated by the level of supportrequired for the blade 25. The top end 38 of each blade is arranged tofollow a circular path which brings it into close proximity to zones atwhich point mulching of the GOM can be facilitated. In the form of themulching machine 10 illustrated, first and second cutting zones areprovided and these include an arrangement employing one or more mulchingblocks or anvils. In FIG. 1, a first anvil 39 is shown in a firstcutting zone 100 with its primary cutting edge disposed at an angle ofapproximately 34° to horizontal. This arrangement is more clearly shownin FIG. 5 in which it is seen that the anvil 39 also includes an anvilcover plate 40. In this figure, the dot outline path of the tips of theblades 25 shows that the tips approach the leading edge 41 of the anvil39 very closely. In practice, the distance between the tips and theleading edge 41 is in the order of 5 mm, although that distance can bealtered to suit the type of GOM being mulched and the type of mulchrequired. Also, the angle at which the anvil 39 is disposed can bealtered for similar considerations.

In the arrangement illustrated, second and third anvils 42 and 43 arealso provided. Like the first anvil 39, the second and third anvils arepositioned in close proximity to the path of travel of the blade tips38. However, the second anvil 42 is positioned so that the closest pointof travel of the blade tip 38 thereto is toward a rear edge 44 thereof,while the closest point of travel of the blade tips to the third anvil43 is at a front edge 49.

The three anvils 39, 42 and 43, and the blades 25 of the hammers 16,effectively chop and mulch GOM which is fed into the mulching machine10.

The machine 10 advantageously offers simple regulation of the treatmentof the GOM, by facilitating control of the speed of the infeed conveyerbelt 11 and conveyer roller 12, and the speed of the cutting mill 15.Such control can be used to regulate the size of mulch product producedby the machine 10.

Each of the anvils 39, 42 and 43 is mounted on a mounting arrangement 46and that arrangement includes a beam 47 which is hinged to the frame 48of the machine 10. The hinged connection 49 facilitates verticalmovement of the mounting arrangement 46, so that any particles that maybe of sufficient hardness to damage the blades or the anvils if theywere to be jammed therebetween, will be accommodated by verticalmovement of the mounting arrangement so that jamming is prevented. Aspring arrangement 50 is employed to maintain the mounting arrangement46 at the desired position, but permits resilient vertical movement ofthe mounting arrangement against the spring bias when required.

The mulching occurs principally due to the action of the blades on theGOM in each of the cutting zones 100 and 200. In the cutting zone 100,the GOM is subject to a first cutting action that cuts the GOM intoparticles. The average length of the particles is determined by therotational speed of the cutting mill 15 and the speed at which the GOMis fed to the first cutting zone 100. It is envisaged that the cuttingmill 15 will rotate at approximately 1600 RPM and the feeding speed ofGOM will be approximately 0.125 m/s to produce particles of an averagelength of 40 mm although smaller and larger particles will be cutbecause not all GOM is fed in a straight line into the zone 100.

The mulch particles are then treated at the second cutting zone 200 andthe arrangement of the cutting mill 15 and the anvil 39 is such as topromote transference of the particles from the first cutting zone 100 tothe second cutting zone 200. That is, the angle at which the blades 25engage the GOM at the anvil 39 promotes movement of the particles to thezone 200. Transference between zones could be effected by other means,but the described arrangement is preferred.

The cut particles are treated at the second cutting zone 200 to completethe mulch product. The anvil 42 serves as a stirrer of the particles,preventing them from building up in front of the anvil 43. The anvil 42plays little or no other part in the mulching process. The blade tipspass into close proximity to the rear edge 44 of the anvil 43 and atthat point, the blade applies a further cutting action to the mulchparticles to further reduce their size, to an average length of 19 mm.

The engagement of the blades 25 with the particles at the second cuttingzone 200 also causes the mulch product to be ejected from the cuttingzone 200 at high velocity due to the rotational velocity of the cuttingmill 15 and this is advantageous for ejecting the mulch product from themachine 10 and for forming a windrow as will be described later.

The machine 10 further employs the addition of water during the mulchingprocess, so that the GOM being mulched can be kept moist. The additionof water to the GOM being treated ensures that the moisture content ofthe mulch product is sufficient for composting of that product to takeplace and the control of the added water can be such as to optimise themoisture content for maximum composting efficiency. Additionally, theaddition of water to the mulch surpresses the generation of dust.

In the machine 10 illustrated, water is injected into the cutting mill15, preferably to an area above the cutting edge of the first anvil 39.Injection of water is preferably controlled to limit the volume which isinjected. Additionally, the injection of water is preferably limited toonly those periods in which GOM is fed through the infeed and conveyorrollers. In a simple form, that control can be by way of a valve whichis opened and closed upon movement of the infeed roller 13, when GOM isfed into the machine 10. For example vertical upward movement of theinfeed roller 13 could cause the valve to open and water to be injectedwhile vertical downward movement will cause the valve to close. Thissystem limits water wastage as well as eliminating the potential forpuddles to form below the machine, or for excess water to be collectedin the windrow.

The water could be injected or otherwise supplied in alternativearrangements and these are within the scope of the invention. What isimportant is that water be available for supply to the mulch prior toits ejection from the machine to a windrow, so that the optimum moisturecontent can be obtained for maximum composting efficiency. The water canalso contain additives, such as fertilisers, as appropriate.

For supplying water in the manner described, water jets 51 are providedand these direct water towards the leading edge 41 of the first anvil39. The injection of water at this point ensures an even and thoroughmixing of water with the mulch particles. The water jets 51 can take anysuitable form as are known in the art. Two jets 51 may be provided atthe position indicated in the roof 52 of the machine 10 which are spacedapart across the width of the cutting mill 15. Further jets may beprovided as necessary such as at the sides of the cutting mill 15.

The water can have an additional function in the machine 10, and that isto act as a cooling medium. Thus, the water can be passed through amanifold in the hydraulic tank which supplies hydraulic fluid to drivevarious driven components of the machine, and this can take place priorto the water being injected into the mulch particles. The water can becirculated to other heated components as necessary to perform a similarcooling function.

The mounting arrangement 46 described earlier, further includes a plate53 upon which each of the anvils 42 and 43 are mounted and which isconnected at one end to the spring arrangement 50. The plate is formedto have two sections 54 and 55 which are arranged at an angle to oneanother. In use, the section 54 is substantially horizontal, while thesection 55 is angled upwardly from the plate 54. The upwardly angledsection 55 is so angled so as to direct mulch product into a deliverychute 56 seen in FIG. 1. The angle of incidence of the section 55 can bearranged as necessary to correctly direct the mulched product.

The delivery chute 56 performs an important function of the machine 10as it directs the mulch for the formation of the windrow. The deliverychute can be hydraulically operated so that the direction of ejection ofmulch can be controlled. For example, at the commencement of thewindrow, the delivery chute can be directed substantially horizontallyand as the height of the windrow increases the angle of the deliverychute can be altered.

The velocity of the mulch product which exits the cutting zone 200 canbe sufficient to be directed along the inclined plate 55 and into thedelivery chute 56 without additional assistance, although suchassistance could be provided in an alternative arrangement. The velocityof the mulch product through the delivery chute 56 is in the region of72 m/s when the cutting mill is rotating at 1600 RPM, although thevelocity can vary depending on the angle at which the delivery chute 56is disposed relative to the angle at which the mulch product enters thechute. The mulch product enters the delivery chute 56 and is directedfrom there to the windrow. This velocity advantageously tends to throwthe larger mulch particles to the outside of the windrow. The deliverychute can have any suitable configuration and may include an extensionwhich extends from the chute shown.

The geometry of the machine 10 illustrated, provides advantageousqualities which contribute to the proper operation thereof. Inparticular, the axes of rotation of each of the conveyor roller 12, theinfeed roller 13 and the cutting mill 15 preferably are arrangedaccording to a preset geometry to ensure optimum particle size anddelivery of mulch. Thus, it is preferable that the axis of the cuttingmill 15 be located in a plane below that of the infeed roller 13, butabove that of the conveyor roller 12. That is the arrangement shown inFIG. 1 and that arrangement promotes passage of GOM toward the firstcutting zone 100 of the machine 10 and the action of the cutting blades15 and the anvil 39 is such as to drag the GOM from the feed facilityand push the cut particles toward the second cutting zone 200.

The machine 10 as above described has several advantages over knownmachines. A primary advantage relates to the absence of screens forparticle size screening. The absence of screens means that no downtimeis created by the need to clean or replaced damaged screens. Downtimefor that purpose occurs relatively frequently in known mulchingmachinery. The absence of screens additionally facilitates bettermaintenance of the machine by enabling easier access to machinecomponents.

A further advantage of the machine 10, is that the moisture content ofthe mulch produced can be accurately controlled by the addition of waterthrough the water jets 51. The provision of water supply means thatwater can be added during mulching so that separate addition after themulch has been produced is not necessary. This is particularlyadvantageous, as the windrow which is formed is ready to commencecomposting immediately and does not require further treatment for thatpurpose.

A still further advantage of the machine is that the mulch particles canbe formed in a size and in a suitably compacted manner in the windrow,in which further treatment of the mulch to facilitate composting thereofis unnecessary. In particular, the mulch product of the machine of theinvention composts to produce a product which meets with therequirements of Australian Standard 4454/1997 with only two turns over a14 day period. Such a composting rate has not been achieved anywhere inthe world to the applicants knowledge in open windrow composting. Thisresult has been achieved by a combination of controlled particle sizeand moisture content and also by the compacted form of windrow created.The compacted windrow is due to the angle of delivery of the mulch andthe speed at which it is delivered, so that it is self compacting. Thespeed of delivery of the mulch is a function of the rotating speed ofthe cutting mill which rotates at speeds of approximately 1600 RPM. Thiscompares with other machinery which runs at approximately 600 RPM. Thus,the mulch is ejected at a far greater velocity and thus impacts thewindrow with a momentum sufficient to have a compacting effect.

The mix of mulch particles processed by the method and apparatus of theinvention provides good aeration and the cutting action to which the GOMis subjected increases the surface area of the particles compared withwindrows formed by conventional methods. That increased surface areaallows easier access of the food substrates to the compostmicro-organisms. There are three types of compost micro-organisms whichfeed on the food substrates, the first of which is called Psychrophilicwhich initiates the composting and in doing so generates heat up to 25°Celsius in the windrow. The second type of compost micro-organism iscalled Mesophilic and this takes over to further the composting, raisingthe temperature of the windrow to approximately 40° Celsius. A thirdcompost micro-organism is called Themiophilic and this raises thetemperature of the windrow to in excess of 70° Celsius.

Adding water via water jets to the mulch particles advantageouslyresults in a moisture content of approximately 38% which is evenlydistributed through out the windrow and which initiates and promotesactivity of the compost micro-organisms. If water were not added, thatactivity could be delayed.

It is desired that the temperature of the windrow be at least 55°Celsius for a period of three days, so as to kill any weed seed orpathogens (disease) that may be present in the green organic materialand this preferred requirement is incorporated into the AustralianStandard 4454/97. As is apparent from the above description, a windrowproduced according to the invention achieves such temperatures and thesecan be maintained for the minimum three day period.

The temperature of the windrow spreads from the centre thereof toapproximately 1 meter from the outside. The windrow sections beyond thistherefore do not generally reach the required composting temperaturesand therefore, it is necessary that the windrow be turned over. Thatprocess involves taking the first meter or so from the outside of thewindrow and placing that mulch to the middle of a new windrow. The otherportions of the original windrow are placed on the outside of the newwindrow. This turning of the windrow takes place a further two times atsimilar intervals and using the same procedure. After the third turn,the composted mulch is ready for use or sale. If the mulch is sittingfor longer than two weeks, it is necessary for the windrow to be aeratedby turning according to the above procedures, to prevent the mulch frombecoming anaerobic. A typical composting period is in the region of 12days.

The results obtained with the invention have been highly favourable.Tests to date have shown that a windrow of the following characteristicscan be consistently produced.

Mulch Particle Size

Classification Actual Size (range mm) Percentage % Fine  0-5 25 Fine 5-19 35 Medium 19-50 30 Medium 50-80 5 Large 80-over 5

Windrow Size (In Meters)

Height Width at base Length 5 6 to 7 10 minimum

Density—approximately 2.25 cubic meters per tonne.

Moisture content—approximately 38%

Oxygen content 8-12% in any part of the windrow

Time for production—approximately 3 hours

Composting period—12 days

A windrow formed according to the invention can be approximately 20%denser than windrows formed by conventional means and with addedmoisture, composts readily, in accordance with the Australian Standard.

The invention described herein is susceptible to variations,modifications and/or additions other than those specifically describedand it is to be understood that the invention includes all suchvariations, modifications and/or additions which fall within the spiritand scope of the above description.

What is claimed is:
 1. A method of processing green organic material (“GOM”) into mulch particles for forming a mulch windrow, including feeding GOM to a first cutting zone and rotating a plurality of blades through that zone to cut the GOM into smaller particles, transferring the particles to a second cutting zone and rotating a plurality of blades therethrough to further reduce their size to a suitable mulch particle size and ejecting said mulch particles from said second cutting zone by the action of said blades of said second cutting zone on said particles, at high velocity directly into a windrow formation, the method further including the addition of moisture to the GOM prior to ejection from said second cutting zone to increase the moisture content of the windrow formed.
 2. A method according to claim 1, wherein moisture is added so that the moisture content of the windrow is about 38%.
 3. A method according to claim 1, wherein water forms the moisture additive.
 4. A method according to claim 3, wherein said water is added adjacent to the first cutting zone.
 5. A method according to claim 1, wherein GOM is fed to said first cutting zone between 0.125 m/s and 0.5 m/s and said blades rotate in the range of 1600 RPM.
 6. A method according to claim 1, wherein mulch particles are ejected at about 72 m/s.
 7. Apparatus for processing green organic material (“GOM”) to form mulch particles for a mulch windrow, said apparatus including a first cutting zone and at least one blade for rotation through said first cutting zone for cutting the GOM into smaller particles, a second cutting zone and at least one blade for rotation through said second cutting zone for cutting said particles to further reduce their size to a suitable mulch particle size, feeding means to feed GOM to said first cutting zone and ejecting means to eject said mulch particles from said second cutting zone at high velocity directly by the action of said blades of said second cutting zone in said particles, into a windrow formation, and means to increase the moisture content of the windrow formed by adding moisture to the GOM prior to ejection from said second cutting zone.
 8. Apparatus according to claim 7, wherein said at least one blade that rotates through said first cutting zone also rotates through said second cutting zone.
 9. Apparatus according to claim 7, wherein said at least one blade is rotatably mounted to said cylindrical mill for rotation relative thereto upon engagement with GOM or a particle or other material through which it is not able to cut.
 10. Apparatus according to claim 7, including guide means for guiding the mulch particles during ejection from said second cutting zone, in a manner facilitating formation of a mulch windrow.
 11. Apparatus according to claim 10, said guiding means including a plate for guiding the mulch particles and wherein said plate is adjustable to adjust the direction in which the mulch particles are directed.
 12. Apparatus according to claim 7, said moisture increasing means including means to supply liquid at or between the feeding means and the ejecting means.
 13. Apparatus according to claim 12, wherein the liquid is water and is supplied through one or more jets.
 14. Apparatus according to claim 7, said feeding means including a conveyor to convey GOM placed thereon to said first cutting zone.
 15. Apparatus according to claim 7, said feeding means including a conveyor belt mounted about one or more conveyor rollers, and an infeed roller rotatably mounted above and at one end of said conveyor belt, said infeed roller and said conveyor belt being positioned relative to one another such that GOM being conveyed on said conveyor belt is gripped between said belt and said infeed roller for feeding to said first cutting zone, said cutting mill being rotatably mounted on an axis spaced from and between the axes of rotation of said infeed roller and the conveyor roller at said one end of said conveyor belt.
 16. Apparatus according to claim 15, wherein said infeed roller is mounted for relative movement away from said conveyor belt to accommodate variations in the bulk of GOM passing therebetween.
 17. Apparatus according to claim 7, said blades rotating past and in close proximity to an anvil in each of said first and second cutting zones to facilitate cutting the GOM and particles respectively.
 18. Apparatus according to claim 17, wherein each of said anvils is mounted for relative movement away from said blades to accommodate variations in the bulk of the GOM or particles passing therebetween. 